1、Designation: D 4729 04Standard Test Method forIn Situ Stress and Modulus of Deformation Using theFlatjack Method1This standard is issued under the fixed designation D 4729; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope*1.1 The flatjack test measures stress at a rock surface. Themodulus of deformation and the long-term deformationalprop
3、erties (creep) may also be evaluated.1.2 All observed and calculated values shall conform to theguidelines for significant digits and rounding established inPractice D 6026.1.2.1 The method used to specifiy how data are collected,calculated, or recorded in this standard is not directly related tothe
4、 accuracy to which the data can be applied in design or otheruses, or both. How one applies the results obtained using thisstandard is beyond its scope.1.3 LimitationThe flatjack test measures the averagestress normal to the surface of the test chamber. Undisturbedstress levels must be determined by
5、 theoretical interpretationsof these data.1.4 Assumptions and Factors Influencing the Data:1.4.1 The stress relief is assumed to be an elastic, reversibleprocess. In nonhomogeneous or highly fractured materials, thismay not be completely true.1.4.2 The equations assume that the rock mass is isotropi
6、cand homogeneous. Anisotropic effects may be estimated bytesting in different orientations.1.4.3 The flatjack is assumed to be 100 % efficient. Thedesign and size requirements of 7.1 were determined to satisfythis requirement to within a few percent.1.4.4 The jack is assumed to be aligned with the p
7、rincipalstresses on the surface of the opening. Shear stresses are notcanceled by jack pressure. Orientating the tests in threedirections in each plane tested prevents the misalignment frombeing excessive for at least one of the tests.1.5 The values stated in inch-pound units are to be regardedas th
8、e standard.1.6 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory requirements prior to use.2.
9、Referenced Documents2.1 ASTM Standards:2D 653 Terminology Relating to Soil, Rock and ContainedFluidsD 2113 Practice for Diamond Core Drilling for Site Inves-tigationD 3740 Practice for Minimum Requirements for AgenciesEngaged in the Testing and/or Inspection of Soil and Rockas Used in Engineering De
10、sign and ConstructionD 5720 Practice of Electronic Transducer-based PressureMeasurement Systems for Geotechnical PurposesD 6026 Practice for Using Significant Digits in Geotechni-cal DataD 6027 Practice for Calibrating Linear Displacement Trans-ducers for Geotechnical Purposes3. Terminology3.1 For t
11、erminology used in this test method, refer toTerminology D 653.3.2 Definitions of Terms Specific to This Standard:3.2.1 cancellation pressurethe pressure in the flatjackrequired to return the rock to its initial position.3.2.2 skin stressthe tangential stress at the surface of anopening.3.2.3 undist
12、urbed stressthe stress field existing in a rockmass prior to excavation of an opening.4. Summary of Test Method4.1 The in situ stress in the rock mass is relieved by cuttinga slot into the rock perpendicular to the surface of the test adit.The deformation caused by this stress relief is measured. Ah
13、ydraulic flatjack is placed into the slot and is pressurized untilthe above-measured displacement is canceled. This reappliedstress is approximately equal to the stress in the rock mass atthe test location in a direction perpendicular to the plane of thejack. The deformational characteristics of the
14、 rock mass areevaluated by incrementally loading the flatjack and measuringthe deformation.1This test method is under the jurisdiction ofASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.12 on Rock Mechanics.Current edition approved Nov. 1, 2004. Published Decem
15、ber 2004. Originallyapproved in 1987. Last previous edition approved in 1997 as D 4729 87 (1997).2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Docum
16、ent Summary page onthe ASTM website.1*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 Tests in Orthogonal DirectionsThe flatjack most ac-curat
17、ely determines the stress parallel to the long axis of theadit, because this stress is the least affected by the presence ofthe opening. (The other tangential stress is highly concen-trated.) In addition, if the adit is in a stress field where one ofthe stresses is significantly larger than the othe
18、rs (3 or 4 times),certain locations in the adit may be in very low compressive oreven tensile stress. Flatjack tests in these locations can giveanomalous and misleading results. Because of these factors, thetest adit should have at least two, and preferably three, long (atleast 4 to 5 times the diam
19、eter), straight sections at about 90to each other. Testing should be distributed evenly in all threesections to provide redundant data and, if results in one sectionare anomalous, to allow the program to produce sufficientusable data.NOTE 1Not withstanding the statements on precision and bias con-ta
20、ined in this test method; the precision of this test method is dependenton the competence of the personnel performing it, and the suitability of theequipment and facilities used. Agencies that meet the criteria of PracticeD 3740 are generally considered capable of competent and objectivetesting. Use
21、rs of this test method are cautioned that compliance withPractice D 3740 does not in itself assure reliable testing. Reliable testingdepends on many factors; Practice D 3740 provides a means of evaluatingsome of those factors.6. Interferences6.1 Personnel Prequalification:6.1.1 Test PersonnelAll per
22、sonnel involved in performingthe test, including the technicians and test supervisor, shall beformally prequalified.6.1.2 Drilling and Sawcut PersonnelQuality drilling andsawcutting is important to achievement of successful flatjacktests. The drilling and sawcut personnel should be capable ofperform
23、ing the precision necessary to successfully produce theslot and instrument holes.6.2 Equipment Performance VerificationThe complianceof all equipment and apparatus with performance specificationsapparatus shall be verified. If no requirements are stated, themanufacturers specifications for the equip
24、ment shall be therequired level of performance. Performance verification isgenerally done by calibrating the equipment and measurementsystems. Calibration and documentation shall be accomplishedaccording to standard procedures such as in Practices D 5720and D 6027.6.3 Local Geologic FeaturesLocal fe
25、atures, particularlyfaults, shear zones, etc., can influence the local stress field.Large inclusions in the rock can affect both the stress anddeformational properties. Test locations should be carefullyselected so that the effects of such features are minimized or, ifthey are the features of intere
26、st, accounted for fully.6.4 Influence of ExcavationsOther excavations intersect-ing the test adit will cause complex stress concentration effectsby superposition. Flatjack tests should be located at least threediameters of the intersecting feature away from that feature. Ifthe test adit is excavated
27、 by conventional methods, then thesurfaces for testing should be further excavated by nonblastingtechniques to remove loose material resulting from stress reliefor blasting.7. Apparatus7.1 FlatjacksFlatjacks shall be designed to operate atpressures of several thousand pounds per square inch whenprop
28、erly installed. The jacks shall be constructed so that thetwo main plates move apart in essentially a parallel mannerover the range of the jack. The range shall be at least 0.25 in.(6 mm). The jacks covered by this standard are square and thearea of the jack shall be no less than 2 ft (0.6 m) wide.N
29、OTE 2Other flat jack shapes are available that may be better suitedfor specific applications. This standard only covers the basic square flatjack, however the basic principles discussed here will still apply.7.2 Instrumentation:7.2.1 PressureElectronic transducers or hydraulic gagesmay be used to mo
30、nitor flatjack pressure. The pressure trans-ducer shall have an accuracy of at least 620 lbf/in.2(60.14MPa), including errors introduced by the readout system and asensitivity of at least 10 lbf/in.2(0.069 MPa).7.2.2 DeformationDeformation measurement devices in-cluding mechanical dial gages, and el
31、ectronic transducers suchas LVDTs or linear potentiometers. The devices can be eitherstationary, or portable depending on the site requirements. Thedeformation device shall have an accuracy of at least 60.0001in. (60.0025 mm) and a sensitivity of at least 0.00005 in.(0.0013 mm).7.2.3 Internal GagesS
32、train gages inside the flatjack shallbe calibrated prior to installation in the jack. The effects of thehydraulic oil and ambient pressure increase on the gages shallbe determined prior to testing.7.3 MortarIf mortar is used to cement the flatjack into theslot, a high-early strength, non-shrink mate
33、rial shall be used.The mortar may include up to 50 % clean sand by weight, withgrain size between 20- and 60-mesh. Clean, potable water shallbe used for the mortar. The cured mortar shall have a strengthgreater than the stress applied by the flatjack. The modulus ofthe mortar may be required to be r
34、emoved from some of thedeterminations of rock modulus.7.4 Sawing EquipmentEquipment used to saw a slot in therock should be of a type where large center or end holes are notrequired. These large holes can cause serious changes in thestress field to be measured.8. Procedure8.1 Groups at Each Test Sta
35、tionAt least one group ofjacks should be tested in each adit section. Each group shouldhave three flatjacks installed horizontally inclined 45 andvertically. The jacks in each group should all be placed in onepart of the adit within 20 ft (6.1 m) of each other along thelength of the adit.8.2 Surface
36、 Preparation:8.2.1 Rock QualityThe flatjack and deformation instru-mentation should not be installed in loose, broken, or drummymaterial. Loose, broken, or drummy material may be detectedby a dull, hollow sound when struck with a hammer; suchmaterial should be removed.8.2.2 DimensionsThe prepared su
37、rface shall extend atleast 1 ft (0.30 m) past either end of the flatjack slot and at leastD47290421 ft (0.30 m) past the furthest measuring points. The transduc-ers or flatjack shall be 1 ft (0.30 m) inside the prepared surfaceat any point (see Fig. 1).8.2.3 MethodDrilling to a uniform depth may be
38、requiredto prepare the rock face. Residual rock between the drill holesmay be removed by moving the bit back and forth until asmooth surface is achieved. Alternatively, in hard, competentrock, controlled blasting with very small charges may be usedto remove the residual rock. In softer material, coa
39、rse grinding,chipping, or cutting devices may be required.8.2.4 SmoothnessIdeally, the prepared surface shall be aplane. The difference between the highest and lowest points onthe prepared surface shall be not greater than 2 in. (50 mm).8.3 Transducer and Measurement Points InstallationTransducers a
40、nd measurement points shall be installed on thecenterline normal to the flatjack, either at the surface or atdepth as shown in Fig. 1. Transducers for stress determinationshall be installed within L/2 of the flatjack slot, where L is thewidth of the flatjack.8.4 Slot CuttingThe slot can be formed by
41、 sawing or bydrilling overlapping holes in weak or highly fractured material.Vibration should be minimized. The slot shall be no more than3 in. (74 mm) wide, and extend no more than 3 in. (75 mm)past the edges of the flatjack. It shall be deep enough that theflatjack may be inserted 3 in. (75 mm) be
42、yond the lowest pointon the rock fact adjacent to the slot. If drilled, care shall betaken that the holes are straight and parallel to keep the bottomof the slot open to receive the jack. The slot shall be washedclean of all dirt and cuttings, using clean water.8.5 Relaxation MeasurementsDeformation
43、 shall be mea-sured immediately upon completion of slot cutting and againimmediately prior to testing. If the rock undergoes strain underconstant load over a period of time, several intermediatereadings shall be taken to evaluate this effect.8.6 Flatjack InstallationFlatjacks shall be centered in th
44、eslot and recessed 3 in. (75 mm) from the face of the excavationto minimize the possibility of rupture during pressurization.The mortar, if used, should surround the jack and shall be freefrom voids. The jack shall be installed to allow sufficient timefor the mortar to attain compressive strength gr
45、eater thanmaximum anticipated jack stress.8.7 Flatjack TestingThe flatjack pressure shall be raisedin 100 lb/in.2(0.7 MPa) increments until cancellation of allmeasuring points has been achieved. Deformation shall be readafter each pressure increment. The peak pressure shall bemaintained for 15 min t
46、o check for time-dependent deforma-tion; deformation readings shall be taken every 5 min. Thepressure shall be reduced in 100 lb/in.2(0.69 MPa) decrementsto zero, with deformation read after every decrement. Zeropressure shall be maintained for 15 min to check for time-dependent deformation; deforma
47、tion readings shall be takenevery 5 min. The cycle shall be repeated at least two moretimes using equal pressure increments and decrements. Thepeak jack stress of these cycles should be as high as possibleand be determined by the test engineer in the field dependingon the jack and rock strength and
48、the cancellation pressure.8.8 Data Recording RequirementsExamples of test datasheets and the type of data to record are shown on Figs. 2 and3. However, the data requirements may be site specific andshall be developed using the minimum requirements specifiedin Section 10, Reports.9. Calculation9.1 Ge
49、neralThe calculation of stress and modulus ofdeformation from flatjack data is influenced by the complexloading geometry of the test. In addition, the load applied bythe flatjack is not the same as the load originally acting on therock. The jack expands in one direction only, so lateral andshear components are not restored. This is particularly signifi-cant when the jack is not aligned with a principal stress.Several elastic models and assumptions have been used tocompensate for these factors, leading to varied and sometimescontradictory methods of dat
